Snapped off my rear dropout!

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markz   100 GW

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Snapped off my rear dropout!

Post by markz » May 21 2015 8:04pm

I snapped off both of my rear dropouts. At first when I powered the thing, the wheel would slip out of its hole. I then decided to cut & file a bigger gap.
Metal is gone! This frame is F@*K3d!

Right now I am emailing a fabrication shop, should I go 1.5" x 1.5" and 1/4" thick alum that is notched to a U shape to hold the spindle/axle in place?
This wont be strong enough will it? Alum is too easy to twist.

But as I think of it just now and some searching, steel is better.
Cant weld alum to steel so so do the same as above...1.5"x1.5" by 1/4" alum, welded on....then bolt on some steel to the alum notching in the spindle/axle.
This is going to basically wipe out any rear derailleur or rear freewheel gears I want.


Kinda like this guy
The attachment mongoose pinch dropout.JPG is no longer available
It might be cheaper for me to buy a steel bike from Nashbar.com for $99 + s/h
http://www.nashbar.com/bikes/Product_10 ... 1___204685
And swap over all my bicycle parts, shifters, bottom bracket etc.

Im tempted to go nashbar, but am hesitant because of the special tools I need to do a swap.

I can imagine these custom fab shops are going to give me a price of $100 or more for a couple alum tabs. I will email away and see what comes of it.
The attachment 20150521_181619[1].jpg is no longer available
The attachment 20150521_181505[1].jpg is no longer available
mongoose pinch dropout.JPG

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beast775   100 kW

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Re: Snapped off my rear dropout!

Post by beast775 » May 21 2015 11:07pm

Sorry to see that :shock: Get a new frame ans start over....if you have a heavy vise-hacksaw-drill-vise grips x2, you can make your own pretty easy.just look around on here for torque arms.or drbass sells deluxe torque arms.
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Re: Snapped off my rear dropout!

Post by speedpower99 » May 22 2015 1:20am

Aluminum is not good for torque arm, too soft.
If you have skill and tools, you can make a steel plate and bolt on your frame. But it looks hard since your original dropout slot is gone.

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Re: Snapped off my rear dropout!

Post by Ch00paKabrA » May 22 2015 6:37am

All you need is a $10.00 piece of 3/8" steel sheet from Lowe's or any other home improvement store, a hacksaw, drill, drill bits, and a file and you can make your own drop outs and bolt them onto that frame.

It really isn't hard; just time consuming. If you have more time than money, go that route. If you have more money than time, then get the nashbar frame but be aware that the dop outs on a steel frame are still too thin and you will still need torque arms.

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Re: Snapped off my rear dropout!

Post by dogman dan » May 22 2015 6:53am

It would seem that you never had a torque arm on the bike.

Get some steel, about 1/4 thick. Make some torque arms that bolt on. But also, look for another bike, on the used market. Steel MTB's used should be relatively easy to find. Or another Alloy one, but get a torque arm on it before you ride.

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Re: Snapped off my rear dropout!

Post by arkmundi » May 22 2015 6:54am

You might want to check out my recent experience of the same, where I've posted a collection of notes on the approach I'm taking. Essentially, good steel torque-arms, metal screws and 3M Scotch-Weld Epoxy Adhesive DP420 Black. You can get Doctorbass' ultimate torque-arms, make your own as suggested, or work-up a diagram to have water-jet cut. Idea is that the torque-arm replaces the dropouts, so must be firmly secured to the frame.
dogman dan wrote:... But also, look for another bike, on the used market. Steel MTB's used should be relatively easy to find. Or another Alloy one, but get a torque arm on it before you ride.
See Letters to my nephew for my collection of notes on finding steel frame bikes on a budget. Current fav is the Trek 820 and I'm actively searching for a used one off Craigslist.

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Re: Snapped off my rear dropout!

Post by 2old » May 22 2015 7:55am

Once a week or so Nashbar has 20-25% off sales which will alleviate the cost.

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TheBeastie   1 MW

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Re: Snapped off my rear dropout!

Post by TheBeastie » May 22 2015 9:21am

Its a shame you can't do something like find some steel drop outs with large tubular bars and slide them over the remaining parts of the aluminium chainstay dropouts of the existing frame like of kind of two fingered steel glove.
Then fill the tube air gap between the steel and aluminium dropouts with glue or maybe even pore molten aluminium down the steel tubes to bond them together.

Just googling "chainstay dropouts" actually does bring up pictures of various attachable dropouts.
https://www.google.com.au/search?q=chai ... 024%3B1024

This guys business appears to be in fixing them
http://gripsport.com.au/index.php/photo ... s-dropouts
http://gripsport.com.au/service/horizontal-dropouts

May ask if you can get these guys to pre weld their dropouts with some of their fatest Chainstays/seatstay tubing, then slide it over and glue/weld it on somehow with the muggyweld stuff..
http://framebuildersupply.com/collectio ... stay-angle

http://www.framebuilding.com/NEWPARTSPA ... opouts.htm
https://www.youtube.com/watch?v=xQOC2BwiJDU
Last edited by TheBeastie on May 22 2015 10:50am, edited 6 times in total.
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wesnewell   100 GW

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Re: Snapped off my rear dropout!

Post by wesnewell » May 22 2015 9:44am

Get a bike with steel dropouts. Bikes with aluminum dropouts are not suitable for a hub motor. Aluminum is too soft and too brittle for the job. That's why I won't buy a bike with aluminum dropouts and put a hub motor on it. In over 15,000 miles with steel dropouts without torque arms, using regen braking I've never had a problem. If I had to use aluminum, the only thing I'd trust would be at least 1/4" steel torque plates bolted and glued to the dropouts with strong epoxy.
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Re: Snapped off my rear dropout!

Post by amberwolf » May 22 2015 3:50pm

Given your previous mentions of the need for torque arms, I'm surprised you never installed any. :(

But, given that the dropouts are already toast, you'll need to make some steel ones to replace them with and bolt around the remains of what's there.

if you just weld stuff onto the alloy frame, without re-heat-treating it, it won't be as strong as it was. I dunno if that means it will fail or not, but you should be aware of the weakening the welding will do to the frame in that area.


Mine is a steel frame so I welded directly to it; in your case you'd need to weld these up in a form that would bolt around your existing frame.

My solution:
http://www.endless-sphere.com/forums/vi ... 1#p1050001

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Chalo   100 GW

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Re: Snapped off my rear dropout!

Post by Chalo » May 22 2015 3:59pm

You made two avoidable mistakes here. First, you used an aluminum frame with a flatted axle hub motor. That's not a good idea. Then, more importantly, It looks like you filed a square-cornered slot in the dropout. The corners of a slot are like a request to "break here, please" when the axle starts prying on them. Don't do that again, no matter what material you use for you frame and/or torque arm.

Start over with a new frame. Aluminum frames have to be heat treated after welding to recover their strength. You'll be begging for another, more severe failure if you weld on that frame without heat treating afterwards. Get a steel frame this time, preferably with chunky plate dropouts. Then back up your dropout slots with torque arms, screwed to the frame eyelets, that have closed ended slots for the axle.
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Re: Snapped off my rear dropout!

Post by markz » May 22 2015 4:20pm

Well you guys did nail it on the head. No torque arms installed, didnt think I would need it for test throttle pulls with me off the bike and lifting the bike up and putting it back down with light throttle pulls.

I bought the steel 1/4" thick and 1/2" wide and some "Permatex" (Steel & Metal Repair, Steel Weld, Steel Reinforced Industrial Strength, 4500psi strength and 4 minute set time.) All intense and purpose to box the axle in with Permatx and bolts.

This is what I think happened in my case. I had the regular dropout holes, in which I installed motor and test ran it with rear wheel in air, maybe some light on ground throttle pulls with me off bike. This I believe broke off a small piece of stock dropout hole. Once I got everything connected, tire installed, controller mounted, batteries duck taped to top tube, wiring all figured out I would bolt the tire in and do a more light throttle with me off the bike but bike on ground, the axle would spin out. A day of thinking, I cut and notched it (probably too much). First throttle pull of same (me off bike, bike on ground), snap. If it would have survived I would have then probably sat on in, in which it would have snapped anyway. Then mount steel bar for $3 from CT and glued it on.

I guess my next step right now is to see what I can do with my steel, glue and bolts... onto whats left of my Aluminum Specialized Rockhopper dropouts. The fab shops want $150/hr.

I think I am going to check out my local community bike shop, bring my magnet and get me a free steel frame that I know will have different head tube and bb. Plus I also think there is no way to mount up a rear derailleur that normally has a bolt-on hanger, to a frame with its own frame mount hanger. Kind of like this nashbar frame.
Clipboard02.jpg

I've already got the Nashbar items in my checkout cart. 26" Cromo frame, 6L handle bar bag, 10L rear rack trunk, 40L pannier (x2 for $22).

Choices, Choices, Choices.

Yeah Nashbar it is. Im concerned though with the rear der. hanger, will my new XT derailleur with its own hanger bolt onto that frame hanger on the nashbar?

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Re: Snapped off my rear dropout!

Post by upward » May 22 2015 6:47pm

I just returned that nashbar frame today. The product listing originally indicated it was an all Cromoly frame. Turns out the rear is hi-ten steel, and from reading online, I believe the dropouts are stamped (weak).

Bought a surly troll frame instead at my local bike shop. Waiting for it to arrive.

markz   100 GW

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Re: Snapped off my rear dropout!

Post by markz » May 22 2015 7:23pm

Well thats good to know about Nashbar so called "Cromo" frame. I was hesitant to buy from them because of the extra oversize/overweight/s&h charge of $70. I would be out $170. Just for a frame. My local used bike shop sells crappy bikes for a min. of $100, however they chuck frames out all the time, and the used parts are like $5 a peice.

I am going to buy some steel from Metal Supermarket, I believe they cut to suit. I figured out I can work around my mistake with some filing flat of alum, and 3 bolts on the chain side, 4 on the brake side. It seems I need 1/8" thick flat, 2-1/4" by 2" square and 1/8"x some obstuse angle shape.
20150522_175736[1].jpg

I will glue it all down and bolt it, then sandwich it with another flat piece with Permatex metal glue and I will be able to get 2 more smaller bolts onto the tubes (chain stay and seat stay) for each side.

Now should I buy Cold Rolled Steel, Hot Rolled Steel, Alloy Steel, Tool Steel
http://metalsupermarkets.com/calgary/metals/

Get it 3" wide "cold rolled" flatbar, so they can easily chop it off at every 3", get 4 pieces in total, then I cut to fit. I think tool steel will be too hard to cut with my jigsaw and metal blades, sounds interesting. They say Alloy Steel is cheaper, I will get quote on both and go from there.

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Chalo   100 GW

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Re: Snapped off my rear dropout!

Post by Chalo » May 22 2015 7:32pm

upward wrote:I just returned that nashbar frame today. The product listing originally indicated it was an all Cromoly frame. Turns out the rear is hi-ten steel, and from reading online, I believe the dropouts are stamped (weak).

Bought a surly troll frame instead at my local bike shop. Waiting for it to arrive.
Hi-ten steel tubes are usually thicker than corresponding chromoly tubes. So they can be equally strong, but stiffer. That's actually good for what you are doing. It's just slightly heavier than chromoly, which is not that relevant.

There is no general rule to apply to stamped vs. forged vs. investment cast dropouts. Avoid thin dropouts, avoid soft dropouts. Stamped or laser cut dropouts can be as strong as any; you must evaluate on a case by case basis.

I'd trust the plate dropouts on my Redline Monocog 29er, for example, over any cast or forged dropouts I've ever seen. I only use them to hold against the reaction torque washer from my 7-speed internal gear hub, but I have spun that axle through the flats in its washer before.

That said, the Troll is a good frame that you won't be sorry to own.
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Re: Snapped off my rear dropout!

Post by MadRhino » May 22 2015 7:37pm

Just find a piece of 1/4" thick steel angle stock, and cut off your dropout plates from it. That is something you can find for free, and solid enough to hold the torque of any hub motor. If you are good with an angle grinder, your bike can ride tomorrow.
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Re: Snapped off my rear dropout!

Post by amberwolf » May 22 2015 7:43pm

That's sort of what I did, and it would probably hold my x5304 without any nuts or even the clamping bolt. ;)

My steel came from stuff being tossed out when a store was remodelling and removed some almost-hand-sized L-brackets that held a frame for a glass wall to the concrete floor. But I've actually seen nearly identical stuff on the side of the road, at Goodwill, and in junk bins at yard sales, recycling yards, etc. Most of which you could get for a buck or two, and some of which already have slots you can widen with a file or grinder to put the axle in.

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Re: Snapped off my rear dropout!

Post by markz » May 22 2015 9:18pm

I just winged it on the IRFAN program, with included paint tool.
Clipboard024.jpg
Red would be the first plate installed. 1/8" seems flush to tubes.
Blue would be second. with a bunch of the Permatex Glue in there.
Pink/Purple, just an after thought, maybe some flat bar on the seat stays and chain stays. Small minimal bolts bolted onto tubes. Might reduce structure stregth.

Then I would notch out the area needed for the hub to fit properly.

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Re: Snapped off my rear dropout!

Post by Stevil_Knevil » May 22 2015 10:33pm

Too soon to tell - but you might be up for MOST Knuckle-Headed move of the year..

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